Remotely monitoring weight or force is typically accomplished with a conventional load cell that utilizes a strain gauge element mounted on some sort of bending beam. The strain gauge element is connected to a bridge circuit to monitor minute changes in resistance that occur as the mounting surface strains. This type of system can be relatively expensive and typically has an analog output which is susceptible to interference in remote applications. A less expensive load cell design approach is to monitor the electrical capacitance between two spring loaded parallel plates. With increased applied force or weight, the plates move closer together and the capacitance between the plates increases which can be electrically monitored.
One problem with this capacitive approach is that the dielectric constant of the air between the plates changes as humidity and temperature change. The capacitance changes resulting from a changing dielectric constant between the plates cannot be distinguished from capacitance changes resulting from plate movement. Sealing the area between the plates and back-filling with a stable, inert gas is prohibitively expensive and negates the advantage of the capacitive approach.